For decades, the oil and gas company Exxon Mobil has waged a public-facing disinformation campaign about human-caused climate change — even as the company’s scientific publications and internal communications acknowledged its reality, a new study says.

Harvard science historian Naomi Oreskes and postdoctoral fellow Geoffrey Supran analyzed internal, scientific, and public-facing communications from Exxon Mobil. They found the vast majority of the company’s peer-reviewed papers and internal documents confirmed that climate change is real and caused by human activity. But Exxon’s communications with the public through paid editorials, or ‘advertorials’, in the New York Times promoted climate skepticism.

This study is the latest in a series of probes investigating whether the oil and gas giant has misled the public and its shareholders about fossil fuel emissions and the reality of climate change. Investigative journalists at Inside Climate News and theLos Angeles Timesrevealed in 2015 that Exxon’s own scientists have known since the 1970s that fossil fuels contribute to climate change. But the company “put its muscle behind efforts to manufacture doubt about the reality of global warming,” Inside Climate News reported.

So Supran and Oreskes read all 187 of the documents, tallying expressions of doubt or certainty in four main categories: whether climate change is real, caused by people, serious, and solvable. They found that 83 percent of peer-reviewed papers Exxon scientists had contributed to and 80 percent of internal documents said that climate change is real, and humans are driving it. But 81 percent of the New York Times advertorials the company bought at $ 31,000 a pop promoted doubt.

“Exxon Mobile [sic] was clearly identified as the source of the advertisements, which met with our advertising acceptability standards,” a spokesperson for the New York Times said in an email. Exxon Mobil did not respond to a request for comment.

The Verge spoke with Supran about his work. “They accused their critics of cherry picking statements,” Supran says. “But we looked at the whole cherry tree. And the trends we found are clear, and evident.”

Partly what prompted these suspicions were investigations by journalists atInside Climate News and the LA Times, which unearthed internal documents, internal memos from the company which they say showed that the company has known for decades about basic climate science and its implications.

In response, the company issued a whole list of articles saying these undercut the allegations against it. It said that journalists “had deliberately cherry picked statements” to come to their conclusions. And so it laid down this challenge for the public. It said: “Read all of these documents, and make up your own minds.”

So we took up that challenge! We thought, “We know how to read.” So, we brought to bear independent, peer-reviewed, established social science methods to consistently and systematically read and interpret all of Exxon’s documents — and that led us to this publication, and this work.

What were those documents?

We looked at 187 documents: all the internal documents unearthed by investigative journalists that formed the basis of their reporting. Plus the peer-reviewed and non-peer-reviewed academic articles put forward by Exxon in rebuttal to the allegations by those journalists.

We also looked at so-called advertorials that Exxon took out in the New York Times. These are op-ed styled advertisements that the company took out for 29 years, every Thursday in the bottom right corner of the op-ed page of the New York Times. Each one cost on average something like $ 31,000 in today’s money. We studied the subset that talked about climate change between change between 1989 and 2004. This was a massive public relations campaign.

How long did this take you?

It’s been a 13-month study, so just over a year. It’s taken awhile, but we got there.

Can you give me some specific examples?`

In 1996, one of Exxon’s climate scientists was a co-author on the famous chapter of the Intergovernmental Panel on Climate Change [report], which concluded: “The body of statistical evidence … now points to a discernible human influence on global climate.” This was the first time when, at the international level, a scientific consensus began to form about the human contribution to climate change.

Then a year later, for example, in 1997 Exxon published an advertorial in the New York Times which said, “Let’s face it: The science of climate change is too uncertain to mandate a plan of action that could plunge economies into turmoil … Scientists cannot predict with certainty if temperatures will increase, by how much, and where changes will occur.”

There are many examples along those lines. That advertorial was called “Reset the alarm.” Others were called, “Unsettled Science.” And in some cases, which we discussed in the paper, these advertorials also expressed explicit, factual misrepresentations. For example, there’s one graph that they showed which, according to the independent scientist who produced the data, described the use of the data as, quote, “very misleading.” That’s the sense of it.

Are you or Dr. Oreskes making any money off of this study? Could you be accused of profiteering?

No. We have an explicit statement of no conflicts of interest at the end of the paper. Naomi is a world-renowned academic at Harvard University, and we’ve conducted peer-reviewed research. I received two months of summer stipend from the Rockefeller Family Fund last July and August, and after that, for a year, have been conducting this research on my own dime. I just finished my PhD, I’m 29, and I live in a shitty student apartment. So if this is what profiteering from my work looks like, I’m not very good at it.

When you were doing this, what was driving you? What change did you want to cause in the world from this paper?

Obviously it’s important to articulate that we’re not lawyers, and this isn’t a legal investigation. Clearly, as I said, Exxon is under scrutiny on multiple legal fronts, and on all those fronts, this same question is being asked: did the company mislead people about climate science and its implications? So the motivation was, we want to get to the bottom of that question.

It’s a very serious allegation to accuse professional journalists of deliberately cherry-picking statements. We realized that’s a testable assertion. So the motivation was to get to the bottom of this, to respond to Exxon’s challenge to read all the documents and make up our own minds. And that’s exactly what we’ve done. And I believe that the results will be of interest to a wide range of people, most probably including some of those investigating any potential wrongdoing.

I’ve devoted my entire adult life to developing technologies to try and address climate change. And to realize that we already have the technologies we need to start tackling this crisis, and yet what we don’t have is the political will to move these technologies out of the lab and into the real world. There’s this bottleneck, and part of the stranglehold on it has been decades of disinformation and climate denial. So that is a powerful motivator to uncover the truth, to expose the reality of Exxon’s contribution to decades of public confusion.